Sven Estridson, Jarl of Denmark, desired independence from King Magnus I of Norway in 1042. Because Magnus was supported by his brother-in-law, Duke Bernard II of Saxony, Sven achieved an alliance with the Obotrites through the mediation of Gottschalk. However, Ratibor was killed in a siege by Magnus in 1043. In an attempt to avenge their father, his sons were killed in the same year in a battle at Lürschau Heath on 28 September.